On Sunday, November 1, 2026, most of the United States will set its clocks back one hour. Many people hope it will be one of the last times.

In July 2026, the U.S. House passed the Sunshine Protection Act by a wide bipartisan margin. The bill would end the twice-yearly clock change by making daylight saving time (DST) permanent. It now sits in the Senate, where its future is uncertain.

Sleep scientists agree with half of that idea. Ending the clock switch is a good move. But the major sleep medicine organizations in the U.S. and abroad say Congress picked the wrong clock. The evidence favors permanent standard time.

This article explains why, what the research shows, where the evidence is still weak, and what you can do to protect your sleep this fall.

The Short Answer

• Your body clock is set mainly by morning light.
• Standard time keeps clock time close to the sun’s time, so you get more light in the morning.
• Permanent DST would move that light to the evening all year, including dark winter months.
• Evening light pushes your body clock later. Your alarm clock does not move with it.
• The result is a small but constant gap between your body clock and your schedule. Sleep experts call this circadian misalignment.
• Every major sleep society that has issued a statement supports permanent standard time.

Your Body Clock Runs on Morning Light

Deep in your brain sits a master clock that runs on a cycle of about 24 hours. It controls when you feel sleepy, when you feel alert, when hormones are released, and how your body handles food.

This clock does not run perfectly on its own. It needs a daily reset, and light is the strongest signal it gets.

Timing matters a great deal:

• Morning light shifts your clock earlier. This helps you fall asleep at a reasonable hour and wake up feeling ready.
• Evening light shifts your clock later. This makes it harder to fall asleep and harder to get up.

Standard time is built to match solar time. Under standard time, the sun is roughly at its highest point around noon on the clock. Daylight is spread more evenly before and after midday, so you get more of the light that keeps your clock on track.

DST moves clock time one hour ahead of the sun. In practice, this trades one hour of morning light for one hour of evening light. For a few summer months, most people tolerate this. Made permanent, that trade would run all year.

What Permanent DST Would Look Like in Winter

Permanent DST sounds like “more sunshine.” It does not add any daylight. It only changes when the clock says the sun rises and sets.

In winter, the effect is easy to see. In cities on the western edge of their time zone, such as Detroit or Seattle, late-December sunrises would land around 9:00 a.m. Children would wait for school buses in the dark. Many adults would start work before sunrise for months.

The U.S. has tried this before. In January 1974, the country moved to year-round DST. Public support dropped quickly during the dark winter mornings, and Congress reversed the change before the year ended.

What the Research Shows

There are no randomized controlled trials on national time policy. A country cannot randomly assign its citizens to different clocks. The best available evidence comes from meta-analyses, large population studies, natural experiments, circadian modeling, and expert consensus statements. That limitation is worth keeping in mind as you read the findings below.

1. The switch itself causes harm

The spring transition costs most people about an hour of sleep and shifts their body clock abruptly.

• Heart attacks. A 2024 meta-analysis of 12 studies from 10 countries found heart attack risk was about 4% higher in the weeks after the spring change. The fall change showed no clear increase.
• Sleep and sleepiness. A 2025 systematic review of 27 studies found that the shift into DST was linked to shorter sleep, worse sleep quality, and more daytime sleepiness. Night owls were hit hardest.
• The fall change is not harmless for everyone. In a study of more than 30,000 Canadian adults aged 45 to 85, people surveyed the week after the return to standard time reported more insomnia and more sleep dissatisfaction than those surveyed the week before.

These findings explain why ending the switch makes sense. They do not, on their own, tell you which permanent time is better. That question depends on what happens when people live on one clock year-round.

2. Living on DST appears to carry ongoing costs

This is where the case for standard time becomes clearer.

• Circadian modeling. A 2025 Stanford study published in PNAS modeled light exposure and body clock strain across the continental U.S. under three policies: permanent standard time, permanent DST, and the current switching system. Switching produced the most strain. Permanent standard time produced the least. When the researchers linked these results to county-level health data, permanent standard time was associated with the largest predicted drop in obesity and stroke. The researchers estimated this could mean roughly 2.6 million fewer people with obesity and about 300,000 fewer strokes compared with the current system. Permanent DST also helped, but only about two-thirds as much.
• Medical errors. A 2024 study of more than 288,000 malpractice claims across three decades found that the DST months were associated with more severe medical incidents and higher payouts than the standard time months.
• Driving fatigue. A 2024 driving simulator study found that signs of fatigue, such as drifting in the lane and longer eye closures, appeared after the spring change and did not fully recover during the following weeks on DST. This was a small study of 37 young adults, so it needs confirmation.
• Your place in the time zone. People on the western edge of a time zone already get later sunlight relative to the clock, which is similar to living on DST. A 2023 study of nearly 2,900 U.S. counties found higher suicide rates in western parts of time zones than in eastern parts, even after adjusting for several social factors. This was an ecological study, so it shows an association, not cause and effect.

Where the Evidence Is Weaker

An honest look at this topic includes the findings that do not fit neatly.

• Heart attack data are mixed. A 2025 JAMA Network Open study of nearly 169,000 patients at more than 1,100 U.S. hospitals found no significant rise in heart attacks during the DST transition weeks. A 2024 Mayo Clinic analysis of 36 million people found only a small, likely unimportant increase after the spring change.
• Some outcomes improve in the fall. A large 2025 study from England found fewer visits for anxiety, depression, heart disease, and sleep disorders in the week after clocks fell back, with little change after the spring shift.
• Evening light has real safety benefits. A 2025 study from the Insurance Institute for Highway Safety found that fatal crashes involving pedestrians and cyclists rose about 13% after the fall change, when evenings got darker. Fatal crashes among drivers and passengers rose 12% after the spring change. Another study predicted that permanent DST would reduce collisions with deer, which peak after dark.

These findings show that the choice involves trade-offs. Evening darkness carries some safety costs, and better street lighting and vehicle safety technology can help address them. Morning darkness, on the other hand, works against the body’s most important daily reset, every day, for everyone.

What Sleep Experts Recommend

The scientific organizations that study sleep and body clocks are in strong agreement.

• The American Academy of Sleep Medicine updated its position in 2024. It states that the U.S. should end seasonal time changes and adopt permanent standard time because it best fits human biology. Many medical and safety groups have endorsed this position.
• The Sleep Research Society issued a 2022 position statement supporting permanent standard time.
• The British Sleep Society reached the same conclusion for the United Kingdom, pointing to the value of natural morning daylight.
• Independent reviews in cardiology, pulmonary medicine, and neurology journals have also concluded that permanent standard time offers the best balance of health and safety.

Arizona Already Lives on Permanent Standard Time

Most of Arizona has stayed on standard time year-round since 1968. Hawaii does the same. The Sunshine Protection Act would let these states keep their current clocks.

Arizona’s long track record shows that a state can run on permanent standard time without major disruption to daily life. Residents never lose an hour of sleep in March, and winter sunrises stay at a reasonable hour.

How to Protect Your Sleep This Fall

Until the law changes, you still have to manage the switch. The fall change is usually easier than the spring change, but it can still throw off your sleep, especially if you are an older adult or already struggle with insomnia.

• Keep your wake time steady. Get up at the same clock time after the change, even if you feel tempted to sleep in.
• Shift gradually if you are sensitive. Move your bedtime and wake time 15 minutes later each night for a few nights before November 1.
• Get bright light soon after waking. Step outside for 15 to 30 minutes within an hour of getting up. Morning light helps your clock settle faster.
• Dim lights in the evening. Lower indoor lighting and limit bright screens in the hour or two before bed.
• Watch for pedestrians at dusk. Evenings get dark suddenly after the change. Drive with extra care around 5 to 7 p.m. If you walk or bike in the evening, wear reflective or bright clothing.
• Talk to a sleep specialist if trouble lasts. Most people adjust within a week. If your sleep stays off for longer than two weeks, an underlying sleep problem may be at play.

If you live in Arizona, your clock will not change. But your calls, flights, and TV schedules with other states will shift by one hour, so plan ahead.

How Strong Is the Evidence?

Question	Type of evidence	Strength
Does the spring switch disrupt sleep?	Systematic review of 27 studies	Moderate to strong
Does the spring switch raise heart attack risk?	Meta-analysis plus large registry studies	Mixed. Any increase appears small
Is a single permanent time better than switching?	Modeling, population studies, expert consensus	Moderate
Is permanent standard time better than permanent DST?	Circadian biology, modeling, natural experiments, expert consensus	Moderate. No trials are possible

The Bottom Line

Ending the twice-yearly clock change is supported by the evidence. The real debate is which clock to keep.

Your body clock depends on morning light. Standard time protects that light. Permanent DST would trade it away for brighter evenings, leaving many Americans with dark mornings for months each year and a body clock that runs slightly behind their schedule.

The research is not perfect, and some outcomes improve with evening light. But the weight of current evidence, along with the consensus of sleep medicine experts, points in one direction. Permanent standard time is the healthier choice.

---

Medical disclaimer: This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. If you have ongoing trouble sleeping or concerns about your health, consult a qualified healthcare provider or a board-certified sleep medicine physician.

---

References

1. Antle, M. C. (2023). The controversy over daylight saving time: Evidence for and against. Current Opinion in Pulmonary Medicine, 29(6), 574–579. https://doi.org/10.1097/MCP.0000000000001003
2. Carter, J. R., Knutson, K. L., & Mokhlesi, B. (2022). Taking to “heart” the proposed legislation for permanent daylight saving time. American Journal of Physiology. Heart and Circulatory Physiology, 323(1), H100–H102. https://doi.org/10.1152/ajpheart.00218.2022
3. Congressional Research Service. (2026). Daylight saving time (DST) (CRS Report No. R45208). https://www.congress.gov/crs-product/R45208
4. Crawford, M. R., Winnebeck, E. C., von Schantz, M., Gardani, M., Miller, M. A., Revell, V., Hare, A., Horton, C. L., Durrant, S., & Steier, J. (2025). The British Sleep Society position statement on daylight saving time in the UK. Journal of Sleep Research, 34(3), e14352. https://doi.org/10.1111/jsr.14352
5. Cunningham, C. X., Nuñez, T. A., Hentati, Y., Sullender, B., Breen, C., Ganz, T. R., Kreling, S. E. S., Shively, K. A., Reese, E., Miles, J., & Prugh, L. R. (2022). Permanent daylight saving time would reduce deer-vehicle collisions. Current Biology, 32(22), 4982–4988.e4. https://doi.org/10.1016/j.cub.2022.10.007
6. de Lange, M. A., Birnie, K., Richmond, R. C., Shapland, C. Y., Eastwood, S. V., Tilling, K., & Davies, N. M. (2025). Acute effects of daylight saving time clock changes on mental and physical health in England: Population based retrospective cohort study. BMJ, 391, e085962. https://doi.org/10.1136/bmj-2025-085962
7. Gao, C., Lage, C., & Scullin, M. K. (2024). Medical malpractice litigation and daylight saving time. Journal of Clinical Sleep Medicine, 20(6), 933–940. https://doi.org/10.5664/jcsm.11038
8. Hurst, A., Morfeld, P., Lewis, P., & Erren, T. C. (2024). Daylight saving time transitions and risk of heart attack. Deutsches Ärzteblatt International, 121(15), 490–496. https://doi.org/10.3238/arztebl.m2024.0078
9. Johnson, K. G., Hale, L., Johnson, D. A., & Malow, B. A. (2024). Daylight saving time harms health and increases inequalities. BMJ, 387, q2335. https://doi.org/10.1136/bmj.q2335
10. Johnson, K. G., & Malow, B. A. (2023). Implications of sleep health policy: Daylight saving and school start times. Continuum, 29(4), 1253–1266. https://doi.org/10.1212/CON.0000000000001331
11. Malow, B. A. (2022). It is time to abolish the clock change and adopt permanent standard time in the United States: A Sleep Research Society position statement. Sleep, 45(12), zsac236. https://doi.org/10.1093/sleep/zsac236
12. Orsini, F., Domenie, E. D., Zarantonello, L., Costa, R., Montagnese, S., & Rossi, R. (2024). Long-term effects of daylight saving time on driving fatigue. Heliyon, 10(15), e34956. https://doi.org/10.1016/j.heliyon.2024.e34956
13. Reis, D. J., Yen, P., Tizenberg, B., Gottipati, A., Postolache, S. Y., De Riggs, D., Nance, M., Dagdag, A., Plater, L., Federline, A., Grassmeyer, R., Dagdag, A., Akram, F., Ozorio Dutra, S. V., Gragnoli, C., RachBeisel, J. A., Volkov, J., Bahraini, N. H., Stiller, J. W., . . . Postolache, T. T. (2023). Longitude-based time zone partitions and rates of suicide. Journal of Affective Disorders, 339, 933–942. https://doi.org/10.1016/j.jad.2023.07.080
14. Rishi, M. A., Cheng, J. Y., Strang, A. R., Sexton-Radek, K., Ganguly, G., Licis, A., Flynn-Evans, E. E., Berneking, M. W., Bhui, R., Creamer, J., Kundel, V., Namen, A. M., Spector, A. R., Olaoye, O., Hashmi, S. D., Abbasi-Feinberg, F., Abreu, A. R., Gurubhagavatula, I., Kapur, V. K., . . . Sullivan, S. S. (2024). Permanent standard time is the optimal choice for health and safety: An American Academy of Sleep Medicine position statement. Journal of Clinical Sleep Medicine, 20(1), 121–125. https://doi.org/10.5664/jcsm.10898
15. Romigi, A., Franco, V., Scoditti, E., Milan, G., Ceriello, F., Centonze, D., & Garbarino, S. (2025). The effects of daylight saving time and clock time transitions on sleep and sleepiness: A systematic review. Sleep Medicine Reviews, 84, 102161. https://doi.org/10.1016/j.smrv.2025.102161
16. Rymer, J. A., Li, S., Chiswell, K., Kansal, A., Nanna, M. G., Gutierrez, J. A., Feldman, D. N., Rao, S. V., & Swaminathan, R. V. (2025). Daylight savings time and acute myocardial infarction. JAMA Network Open, 8(9), e2530442. https://doi.org/10.1001/jamanetworkopen.2025.30442
17. Satterfield, B. A., Dikilitas, O., Van Houten, H., Yao, X., & Gersh, B. J. (2024). Daylight saving time practice and the rate of adverse cardiovascular events in the United States: A probabilistic assessment in a large nationwide study. Mayo Clinic Proceedings: Innovations, Quality & Outcomes, 8(1), 45–52. https://doi.org/10.1016/j.mayocpiqo.2023.12.006
18. Weed, L., & Zeitzer, J. M. (2025). Circadian-informed modeling predicts regional variation in obesity and stroke outcomes under different permanent US time policies. Proceedings of the National Academy of Sciences, 122(38), e2508293122. https://doi.org/10.1073/pnas.2508293122
19. Woods, A. N., Weast, R. A., & Monfort, S. S. (2025). Daylight saving time and fatal crashes: The impact of changing light conditions. Journal of Safety Research, 93, 200–205. https://doi.org/10.1016/j.jsr.2025.02.010
20. Zolfaghari, S., Cyr, M., Pelletier, A., & Postuma, R. B. (2023). Effects of season and daylight saving time shifts on sleep symptoms: Canadian Longitudinal Study on Aging. Neurology, 101(1), e74–e82. https://doi.org/10.1212/WNL.0000000000207342